1. Field of the Invention
This invention generally relates to wireless communication antennas and, more particularly, to a pseudo-fractal antenna system and method using elements of fractal geometry.
2. Description of the Related Art
As noted in U.S. Pat. No. 6,140,975 (Cohen), antenna design has historically been dominated by Euclidean geometry. In such designs, the closed antenna area is directly proportional to the antenna perimeter. For example, if one doubles the length of an Euclidean square (or “quad”) antenna, the enclosed area of the antenna quadruples. Classical antenna design has dealt with planes, circles, triangles, squares, ellipses, rectangles, hemispheres, paraboloids, and the like, (as well as lines). Similarly, resonators, typically capacitors coupled in series and/or parallel with inductors, traditionally are implemented with Euclidian inductors. The prior art design philosophy has been to pick a Euclidean geometric construction, e.g., a quad, and to explore its radiation characteristics, especially with emphasis on frequency resonance and power patterns. The unfortunate result is that antenna design has far too long concentrated on the ease of antenna construction, rather than on the underlying electro-magnetics.
One non-Euclidian geometry is fractal geometry. Fractal geometry may be grouped into random fractals, which are also termed chaotic or Brownian fractals and include a random noise components, or deterministic fractals. In deterministic fractal geometry, a self-similar structure results from the repetition of a design or motif (or “generator”), on a series of different size scales.
Experimentation with non-Euclidean structures has been undertaken with respect to electromagnetic waves, including radio antennas. Prior art spiral antennas, cone antennas, and V-shaped antennas may be considered as a continuous, deterministic first order fractal, whose motif continuously expands as distance increases from a central point. A log-periodic antenna may be considered a type of continuous fractal in that it is fabricated from a radially expanding structure. However, log periodic antennas do not utilize the antenna perimeter for radiation, but instead rely upon an arc-like opening angle in the antenna geometry.
Unintentionally, first order fractals have been used to distort the shape of dipole and vertical antennas to increase gain, the shapes being defined as a Brownian-type of chaotic fractals. First order fractals have also been used to reduce horn-type antenna geometry, in which a double-ridge horn configuration is used to decrease resonant frequency. The use of rectangular, box-like, and triangular shapes as impedance-matching loading elements to shorten antenna element dimensions is also known in the art.
Whether intentional or not, such prior art attempts to use a quasi-fractal or fractal motif in an antenna employ at best a first order iteration fractal. By first iteration it is meant that one Euclidian structure is loaded with another Euclidean structure in a repetitive fashion, using the same size for repetition.
Antenna designed with fractal generators and a number of iterations, which is referred to herein as fractal geometry, appear to offer performance advantages over the conventional Euclidian antenna designs. Alternately, even if performance is not improved, the fractal designs permit antennas to be designed in a new form factor. However, the form factor of a fractal antenna need not necessarily be smaller than a comparable Euclidian antenna, and it need not fit within the constraints of a portable wireless communication device package.
It would be advantageous if fractal geometry could be used in the design of antennas, to fit the antenna form factor within predetermined package constraints.
It would be advantageous if parts of an antenna's radiator could be shaped using fractal geometry, but other parts of the radiator shaped using non-fractal geometry to fit predetermined package constraints.